1. Field of the Invention
The present invention relates to devices and methods for attaching tubes to the inner walls of receiving bores, and more particularly to devices and methods for swaging tubes into the bores of a tube plate by radially expanding each tube under the action of internal pressure introduced into the tube by means of an expansion core and a highly pressurized hydraulic pressure medium.
2. Description of the Prior Art
Tube anchoring methods and devices of the above-mentioned kind are particularly suitable for the expansion-swaging of tube ends into the receiving bores of the tube plates of a heat exchanger, for example. It has been suggested in the past to attach the tubes of a heat exchanger tube cluster to the receiving bores of a tube plate in a swaging operation performed by means of expansion rollers or cores, or in a welding operation, the latter being in some cases combined with a swaging operation.
In recent years, it has further been suggested to utilize the pressure generated by the detonation of an explosive to expansion-swage a hollow body against the inner wall of a receiving bore or cavity. Still another known method of achieving an expansion-swaging effect involves the utilization of ice, where a core is introduced into the end portion of the tube, and the annular space between the core and the tube is filled with pressurized ice water which is then left to solidify. Since the ice water expands as it solidifies, it causes the tube to expand accordingly, thereby producing the desired swaging effect against the bore of the tube plate. A shortcoming of this method, however, is the fact that the degree of expansion and the swaging forces thereby obtainable are restricted to a very narrow range, controlled by the exact volume increase. It is a fact that the maximum pressure which is achievable through the freezing of water inside a closed container is approximately 2000 kp/cm.sup.2. For many applications, however, this pressure is still inadequate.
The use of explosives for the purpose of expansion-swaging has the disadvantage that the forces generated cannot be controlled sufficiently well to obtain consistently even deformations and reliably swaged connections.